1. Field of the Invention
The present invention relates to pharmacological analysis, and particularly to a disposable device capable of producing simultaneous electrochemical and electron paramagnetic resonance spectroscopic measurements.
2. Description of the Related Art
As medicine continues to advance, the analysis of medications is becoming a more significant component as to safer drugs. Analytical chemistry, the field of analyzing the separation, identification, and quantification of chemical compounds, is providing a path for more effective and safer drugs. Two common instrumental methods used in analytical chemistry laboratories are Spectroscopy and Electrochemical analysis.
Spectroscopy is a technique measuring an electromagnetic radiation component that is emitted, absorbed, or scattered by the material being analyzed. Spectroscopy in the pharmaceutical arena can be used to determine impurities of a drug, characterize the composition of a compound, and investigate the interaction of drug metabolites in bodily fluids. Spectroscopy based on measuring microwave absorption includes a technique called Electron Paramagnetic Resonance (EPR), also known in the field as Electron Spin Resonance (ESR).
EPR spectroscopy works by analyzing the unpaired electrons of a sample. A sample of the compound to be tested is placed within a cavity of the EPR Spectrometer surrounded by electromagnets. As a negatively charged electron spins, also referred to as “resonated”, a random magnetic moment is created. When a magnetic field is applied by the surrounding electromagnets, the magnetic field forces the random magnetic moments to line up with the magnetic field. A microwave generator, typically referred to as a Klystron, then pulses the sample with a short burst of waves. These microwaves are absorbed and transmitted through the sample to a receiver on the other end that detects the signal from the sample.
EPR spectroscopy is ideal for any sample that contains unpaired electrons, often referred to as being “paramagnetic” species. Such paramagnetic species include transition metal ions, biradicals, and triplet excited states of diamagnetic molecules. EPR spectroscopy is also ideal for oxidation and reduction reactions, i.e. Redox reactions, where electrons are either added or removed.
Electrochemical analysis, also referred to as electroanalysis, can be of various different forms and types. One such technique is Voltammetry. Voltammetry is a method of determining the chemical makeup of a sample substance by measuring electrical activity, or the accumulation of chemicals, on electrodes placed in the substance. In a two electrode setup, the electrochemical cell generally has a working electrode, a reference electrode, a supporting electrolyte, and an analyte. The analyte is the substance whose properties are measured or analyzed. The working electrode makes contact with the analyte and the reference electrode applies a desired potential in a controlled manner which facilitates the transfer of charge to and from the analyte.
Various issues can arise in using an EPR spectroscopy process for pharmacological analysis that can make EPR spectroscopy relatively prohibitive. If the sample to be analyzed isn't already in a paramagnetic state, then the sample needs to be prepared to be in such paramagnetic state prior to insertion into an EPR spectrometer. Further, if the sample needs preparation via a Redox reaction using an electrochemical cell, other issues can arise. These issues include the type of electrode employed in the electrochemical cell, placement of the cell within the EPR Spectrometer, the complex arrangement of the electrochemical cell, and a relatively prohibitive cost of replacing electrochemical cells for each new electrochemical reaction and analysis, for example.
If a sample is prepared through a Redox reaction, the electrochemical reaction occurs inside the spectroscopic cell as opposed to outside the cell. A benefit of having the electrochemical reaction within the spectroscopic cell is that less stable radicals are typically not lost in the transferring process from one cell to the other. Known electrochemical cells are generally structured in a relatively complex arrangement of multiple compartments with multiple electrodes. Multiple compartments generally increase the surface area of the cell, and thereby can limit the ability to insert the cell into resonator cavities of EPR spectrometers. Further, multiple compartments and multiple electrodes can increase the cost of each cell since more material is typically being used for the cell. Also, a clean cell is desirable for each analysis and, a new cell is therefore desirable in this regard for each analysis to assist in avoiding contamination and to reduce the likelihood of unreliable results for the analysis. Further, replacing these cells time and time again can be relatively costly.
Known electrochemical cells employ base metals and precious metals as the working electrode. While these types of materials can produce the requisite oxidation needed, the oxidation values that are produced are usually not as significant as compared to other electrodes made from different materials. Further, using materials, such as copper and silver, as the working electrode can increase the cost of the electrochemical cell because of the relatively high costs of these raw materials.
It is therefore desirable that a cell used in EPR spectroscopy analysis generate a Redox reaction that also produces optimum oxidation yields, can be used within an EPR spectrometer, is relatively simple to implement, can additionally provide electrochemical analysis, and can be more cost effective as to replacement cells.
Thus, a disposable cell for simultaneous electrochemical and EPR measurements addressing the aforementioned problems is desired.